Apparatus to place a web portion, selectively, above or below another web portion are well known, and usually uses vertically staggered turning bars, which can be rotated in pairs by 90.degree.. These turning bars, for smooth and low wear handling, are formed with perforations or exit openings for air jets at the side about which the web is looped, so that the web, effectively, can be supported by a thin air cushion.
Turning bar systems can be used, for example, when one web portion is to be guided beneath the turning bars, without turning-over or otherwise changing its path for further application to a folding apparatus. The other web portion is guided over the turning bars so that it will be in alignment and stacked over or superposed on the first web portion.
It may occur that production changes require that the previously deflected web portion is to pass straight through the system, whereas the previously deflected turning bar is to be deflected.
Different, selective use of the turning bar system introduces a problem, namely that, upon changing the relative paths of the web portions, the exit openings for the air blasts, upon change-over, will no longer be on the side of the turning bar about which the web is looped. In order to ensure that the web will be supported by an air cushion, it is then necessary to remove the turning bars or turning bar tubes from their holders, turn them about their axes by 180.degree., and then, after resetting the turning bar tubes 90.degree. changed in orientation with respect to the previous setting, that is, rotated 90.degree. about an axis perpendicular to the longitudinal axis of the tube, to re-assemble the turning bar tubes, together with the air supply. This is complicated, takes time, is very labor-intensive, and can only be carried out by hand by operators. Change of the orientation of the--hollow--turning bars by 90.degree. rotation about their vertical axis, thus, cannot be merely automatically commanded, for example from a remote control command console; manual rotation of the turning bars about their longitudinal axis is, additionally, necessary.